Turbulence-dampened float control

ABSTRACT

A standpipe extending upward from the bottom of a liquid container is provided with external helical square threads. A float fits over the standpipe and has a standpipe-operating rod extending down through the standpipe to a control switch below the container. The switch controls a valve for filling the container with liquid to a predetermined liquid level. The float is provided with a sheet metal nut having inwardly projecting teeth engaging the helical threads for rotating the float as the changing liquid level raises and lowers the float relative to the standpipe.

United States Patent Simmons [54] TURBULENCE-DAMPENED FLOAT CONTROL [72]inventor: Edward C. Simmons, Dayton, Ohio [73] Assignee: General MotorsCorporation, Detroit,

, Mich. I

[22] Filed: Nov. 16, 1970 21 Appl. No.: 89,824

[52] 11.5. CI ..137/429, 251/64 [51] Int. Cl. ..G05d 9/12 [58] Field ofSearch l37/409,4l0, 429,430,431,

[56] References Cited I UNITED STATES PATENTS 1,653,688 12/1927Alexander et al ..137/429 X 2,586,619 2/1952 Davis ..137/429 X 1 Feb.22, 1972 2,621,666 12/1952 Omas ..l34/57D 3 ,464,437 9/1969 Zane 137/387 Primary Examiner-M. Cary Nelson Assistant Examiner- -David R.Matthews Attorney-William S. Pettigrew and Frederick M. Ritchie 57ABSTRACT A standpipe extending upward from the bottom of a liquidcontainer is provided with external helical square threads. A float fitsover the standpipe and has a standpipe-operating rod extending downthrough the standpipe to a control switch below the container. Theswitch controls a valve for filling the container with liquid to apredetermined liquid level. The float is provided with a sheet metal nuthaving inwardly projecting teeth engaging the helical threads forrotating the float as the changing liquid level raises and lowers thefloat relative to the standpipe.

4 Claims, 5 Drawing Figures PAIENTEDFEBZZ I972 SHEET 2 []F 2 INVENTOR.lzu/ard 6 Simmons ATTORNEY TURBULENCE-DAMPENED FLOAT CONTROL Thisinvention relates to float controls and, more particularly, to floatcontrols in rapidly changing bodies of liquid or in liquid in which thesurface is churning or rough, thereby causing bobbing of the floatcontrols. A typical environment suitable for use with this invention isa dishwashing chamber and, more particularly, the fill system therefor.

It has been found in bodies of rapidly circulating or churning liquid,the surface of the liquid is apt to be very rough causing rapid andrepeated bobbing of the float control resulting in various switch andcontrol problems such as momentary contacting and irregular coordinationof fill "to achieve a desired liquid level as well as ineffectivenessand unreliability in controlling the liquid level against overfill. Afurther problem existswhere a bobbing float controls electrical flowthrougha switch. The momentary interruption of such electrical flow atthe switch causes interference with radio and television reception.

Accordingly, it is an object of this invention to provide a floatcontrol for a liquid fill system which minimizes the effect of a roughliquid surface on the fill system and which will minimize the bobbing ofthe float adjacent the liquid surface.

It is another object of this invention to provide'a float control whichwill be substantially responsive to the predetermined desired liquidlevel and which will effectively and reliably control to said liquidlevel regardless of the circulation and the churning and the roughnessof the surface of the liquid.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown. I

In the'drawings:

FIG. l is a fragmentary, vertical, sectional view, partly in elevation,through a dishwasher embodying a float control incorporating one form ofmy invention;

FIG. 2 is an enlarged vertical, sectional view, partly in elevation, ofthe float control shown in FIG. 1 with the float in its tub-filledposition (solid line) and its tub-empty position (phantom line);

FIG. 3 is a bottom sectional view of the float and guide takensubstantially along the line 3-3 of FIG. 2;

FIG. 4 is a fragmentary side sectional view taken substantially alongthe line 4-4 of FIGS. 2 and 3 showing a portion of the float and thestandpipe guide; and

FIG. 5 is a perspective view of the sheet metal nut shown in FIGS. 3 and4.

For the purpose of illustrating one application ofmy invention, there isshown in FIG. 1 a portion of a dishwasher including upright side walls22-forming a dishwashing chamber 23 and provided with a bottom wall 24forming a tub sump or liquid container 25. The dishwasher is providedwith a fill control device comprising a fill valve 26 actuated'by asolenoid 27. The fill control device controls the flow of liquid througha supply pipe 28, airgap and trap 30 and then through an entrance 32leading to the liquid chamber or tub sump of the dishwasher. Thedishwasher includes a pump, not shown, which pumps liquid from the sump25 into the rotating spray member 34 which rotates and sprays the liquidonto the dishes which are held in the dish basket 36. The basket 36 maybe supported on rollers 38 operating in a track 40 so that the basket isremovable from the dishwashing chamber. Additional dishwasher structuresuitable for use with my invention is described in US. Pat. No.3,292,645, granted Dec. 20, 1966.

In such a dishwasher, it is customarily desired to stop the inflow ofliquid when the liquid reaches a certain predetermined level within thesump 25. Frequently, it is desired that this fill control operatesatisfactorily even when the pump is in operation circulating the liquidin the dishwashing chamber. I have provided a float control for thispurpose which includes the till control device and is designatedgenerally by the reference numeral 42. In addition to the fill controldevice, the float control comprises a float 44 in the general form of aninverted cup which may be formed of a suitable lightweight plasticmaterial such as polypropylene or polyethylene or polystyrene orpolyurethane foam, for example. This float includes a slightly conicalouter wall46 and an inner vertical cylindrical wall 48 forming a socket.Radial vanes or partitions 50 join the inner cylindrical wall 48 withthe slightly conical outer wali 46 and a circular integral disk-shapedtop wall 52 forming the covering member between the cup-shaped outerwall 46 and the inner cylindrical wall 48. The cylindrical wall 48extends to a closed portion located a substantial distance above the topwall 52. This closed top portion connects to a downwardly extending,control actuating rod portion 54.

The float control also includes a combined rotational and linear guidemeans 56 in the form of a hollow, threaded, upright standpipe 57. Theupright standpipe has a tapered flange 58 at its bottom which rests upona gasket 59 which, in turn, rests upon the tub bottom wall 24. Below thetapered flange 58 is a threaded portion 60 extending through the gasketand the aperture in the tub bottom 24 as well as through an aperture ina control support bracket 62. Beneath the control support bracket 62,the threaded portion is provided with a fastening nut 64 to fasten theguide means 56 to the bottom of the tub. The control support bracket 62is provided with a sensitive microswitch 66 which may be single throw,single pole connected between an electrical power supply and thesolenoid 27 to provide the necessary control of the fill valve 26. Thisswitch 66 is provided with an operating plunger 68, preferably springpressed upwardly against an operating lever or arm 70 extendinglaterally across the axis of the standpipe in the linear guide means 56.The rod 54 extends down through the hollow interior of the standpipe andis guided thereby to rest upon or otherwise operably connect with theoperating lever 70 of the switch 66.

Theassembly of the float control to the dishwasher allows for removal ofthe float for cleaning. With dish rack 36 removed, the float 44 merelylifts off the upright standpipe guide means 56. The guide means 56 isindependently attached to the bottom wall 24 in advance of locating thefloat was found that the fill control would operate satisfactorily whenthe liquid was relatively quiescent within the tub. However, during filland recirculation periods when the liquid was churning and recirculatingrapidly, there was considerable turbulence in the dishwashing chamber.Such turbulence caused the prior art float to bob rapidly up and downthereby causing erratic and false indications of the liquid level in thesump and momentary making and breaking of the contacts of the switch 66.

According to my invention, to prevent this objectionable bobbing due tothe turbulence of the liquid, 1 provide a set of double square helicalthreads 72 on the outer surface of the standpipe of the guide means 56and a nut 74 on the float 44 for controlling the rotation of said float.I noted that when the mass of liquid circulated past and around thefloat 44, this action tendedto impart a slight rotary motion to thefloat in the counterclockwise direction (viewed from above). Inasmuch asthe liquid in the sump during the period of turbulence tends to swirl inthe same counterclockwise direction about the guide means 56, aright-hand thread on the standpipe would provide an additive liftingefiect on the float-swirl plus rising fill level. It is preferable tohave liquid level or depth alone influence the motion of the float.For-this reason, it was found desirable to make the threads 72 aleft-handed thread. The lift due to liquid swirl in the dishwashingchamber was cancelled and float motion was dampened. The threads have a0.57l pitch (1% threads per inch) to provide the correct combination oflift and drag consistent with smooth float motion. The stand- Betweenthe float 44 and the square thread 72 there is provided a sheet metalnut 74 shown in FIG. 5. It is preferably formed of thin stainless steel.it includes an irregular central aperture 76 provided with tangentiallyextending projections 78 which loosely engage the threads 72. The nut 74is also provided with two outwardly and upwardly extending arms 80provided with slots 82 substantially in the shape of arrowheads whichare adapted to receive and grip a pair of diametrically opposite 'vanesor partitions 50 of the float 44, as is particularly shown in FIG. 4.

With this nut 74 so coupling the float 44 to the threads 72, the float44 will be forced 'to rotate as it rises and falls with the changinglevel of the liquid above the bottom wall 24 of the tub. This introducesrotational inertia which acts to regulate the upward and downwardmovement of the float so as to minimize the irregular bobbing of thefloat when the liquid level changes rapidly and is rough and turbulent.I have found that the rotational inertia introduced into the floatcontrol by the guidance of the thread 72 introduces a particularlyeffective form of dampening. Such dampening effectively controlsundesirable float bobbing so that my invention is also useful in manyother liquid level responsive control applications.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

1 claim:

1. A float control including a float adapted to float adjacent a liquidsurface, a combined rotational and linear guide means including threadmeans for guiding the movement of said float substantially along apredetermined linear path perpendicular to said liquid surface withcoincidental controlled rotation of said float to dampen movement ofsaid float along said linear path as the level of said liquid surface ischanged, and a control device operably connected to and operated by saidfloat through said guide means coincidentally to the movement of saidfloat along said predetermined linear path.

2. A float control including a float adapted to float adjacent thesurface of a liquid which is subjected to rotary circulation in onedirection, guide means for guiding the float substantially in apredetermined linear path when the level of the surface of the liquid isincreased, said guide means including helical thread means, nut meansengaging the helical thread means and cooperating with said float forrotating said float coincidentally to the movement of said float alongsaid linear path, said thread means being adapted in cooperation withsaid nut means to move said float rotatingly downwardly when said nutmeans to move said float rotatingly downwardly when said float isrotating in the same direction as said liquid and rotatingly upwardlywhen said float is rising with the increasing level of the liquidsurface whereby to cancel the effect of said rotary circulation on theability of said float to float adjacent the surface of said liquid, anda control device operably connected to and operated by said floatcoincidentally to the movement of said float along said linear path.

3. A float control including a float adapted to float adjacent a liquidsurface above a liquid container wall, guide means for guiding the floatsubstantially in a predetermined linear path perpendicular to saidliquid surface as the level of said liquid surface is changed, saidguide means comprising a hollow standpipe extending from said liquidcontainer wall to a point above said liquid surface and including on theoutside thereof helical thread means extending coaxially relative tosaid linear path, said float comprising an inverted cup having anintegral socket fitting over said standpipe and a nut connected to saidsocket and in threaded engagement with said thread means, whereby saidfloat is caused to rotate coincidentally with its movement along saidlinear path, a control device below said liquid container wall adjacentsaid standpipe and having an operating arm underlying said standpipe,and a rod integral with said float and depending from said socketthrough said hollow standpipe and operably biasing said operating arm ina point contact to facilitate relative rotation between said rod andsaid operating arm, said rod be ing operated by said float to operatesaid control device coincidentally to the movement of said float alongsaid linear path.

4. In combination with a dishwashing chamber having a sump, fill valvemeans for filling said sump with liquid to a predetermined surfacelevel, and means for circulating said liquid in said chamber in a mannerwhich effects rotary circulation of liquid in said sump in onedirection, a float control for said fill valve means including a floatadapted to float adjacent the surface of said liquid, guide means forguiding the float substantially in a predetermined linear pathperpendicular to said liquid surface as the level of said liquid surfaceincreases to said predetermined level, said guide means comprising ahollow standpipe extending from said sump to a point above said liquidsurface and including on the outside thereof helical thread meansextending coaxialiy relative to said linear path, said float comprisingan inverted cup having an integral socket fitting over said standpipeand a nut connected to said socket and in threaded engagement with saidthread means, whereby said float is caused to rotate coincidentally withits movement along said linear path, a control device operably connectedto said fill valve means and operable to close said fill valve meanswhen said liquid surface is at said predetermined surface level, saidcontrol device being below said liquid container wall adjacent saidstandpipe and having an operating arm underlying said standpipe, and arod integral with said float and depending from said socket through saidhollow standpipe and operably biasing said operating arm in a pointcontact to facilitate relative rotation between said rod and saidoperating arm, said rod being operated by said float to operate saidcontrol device coincidentally to the movement of said float along saidlinear path, said helical thread means being adapted in cooperation withsaid nut to move said float rotatingly downwardly when said float isrotating in the same direction as said liquid in said sump androtatingly upwardly when said float is rising with the increasing levelof the liquid surface as said sump is filled whereby to cancel theeffect of said rotary circulation on the ability of said float to floatadjacent the surface of said liquid.

1. A float control including a float adapted to float adjacent a liquidsurface, a combined rotational and linear guide means including threadmeans for guiding the movement of said float substantially along apredetermined linear path perpendicular to said liquid surface withcoincidental controlled rotation of said float to dampen movement ofsaid float along said linear path as the level of said liquid surface ischanged, and a control device operably connected to and operated by saidfloat through said guide means coincidentally to the movement of saidfloat along said predetermined linear path.
 2. A float control includinga float adapted to float adjacent the surface of a liquid which issubjected to rotary circulation in one direction, guide means forguiding the float substantially in a predetermined linear path when thelevel of the surface of the liquid is increased, said guide meansincluding helical thread means, nut meanS engaging the helical threadmeans and cooperating with said float for rotating said floatcoincidentally to the movement of said float along said linear path,said thread means being adapted in cooperation with said nut means tomove said float rotatingly downwardly when said nut means to move saidfloat rotatingly downwardly when said float is rotating in the samedirection as said liquid and rotatingly upwardly when said float isrising with the increasing level of the liquid surface whereby to cancelthe effect of said rotary circulation on the ability of said float tofloat adjacent the surface of said liquid, and a control device operablyconnected to and operated by said float coincidentally to the movementof said float along said linear path.
 3. A float control including afloat adapted to float adjacent a liquid surface above a liquidcontainer wall, guide means for guiding the float substantially in apredetermined linear path perpendicular to said liquid surface as thelevel of said liquid surface is changed, said guide means comprising ahollow standpipe extending from said liquid container wall to a pointabove said liquid surface and including on the outside thereof helicalthread means extending coaxially relative to said linear path, saidfloat comprising an inverted cup having an integral socket fitting oversaid standpipe and a nut connected to said socket and in threadedengagement with said thread means, whereby said float is caused torotate coincidentally with its movement along said linear path, acontrol device below said liquid container wall adjacent said standpipeand having an operating arm underlying said standpipe, and a rodintegral with said float and depending from said socket through saidhollow standpipe and operably biasing said operating arm in a pointcontact to facilitate relative rotation between said rod and saidoperating arm, said rod being operated by said float to operate saidcontrol device coincidentally to the movement of said float along saidlinear path.
 4. In combination with a dishwashing chamber having a sump,fill valve means for filling said sump with liquid to a predeterminedsurface level, and means for circulating said liquid in said chamber ina manner which effects rotary circulation of liquid in said sump in onedirection, a float control for said fill valve means including a floatadapted to float adjacent the surface of said liquid, guide means forguiding the float substantially in a predetermined linear pathperpendicular to said liquid surface as the level of said liquid surfaceincreases to said predetermined level, said guide means comprising ahollow standpipe extending from said sump to a point above said liquidsurface and including on the outside thereof helical thread meansextending coaxially relative to said linear path, said float comprisingan inverted cup having an integral socket fitting over said standpipeand a nut connected to said socket and in threaded engagement with saidthread means, whereby said float is caused to rotate coincidentally withits movement along said linear path, a control device operably connectedto said fill valve means and operable to close said fill valve meanswhen said liquid surface is at said predetermined surface level, saidcontrol device being below said liquid container wall adjacent saidstandpipe and having an operating arm underlying said standpipe, and arod integral with said float and depending from said socket through saidhollow standpipe and operably biasing said operating arm in a pointcontact to facilitate relative rotation between said rod and saidoperating arm, said rod being operated by said float to operate saidcontrol device coincidentally to the movement of said float along saidlinear path, said helical thread means being adapted in cooperation withsaid nut to move said float rotatingly downwardly when said float isrotating in the same direction as said liquid in said sump androtatingly upwardly when said float is rising with the inCreasing levelof the liquid surface as said sump is filled whereby to cancel theeffect of said rotary circulation on the ability of said float to floatadjacent the surface of said liquid.